Vacuum treatment of metals



J. O. BETTERTON ET AL VACUUM TREATMENT OF METALS Filed Oct. l2, 1953 2 Sheets-Sheet l Sept. 22, 1936.

2 Sept 22, 1936-. J. o. BETTERTON ET A1.

VACUUM TREATMENT OF METALS Filed Oct. l2, 1933 2 Sheets-Sheet 2 lNvENToRs .fesse d Bader/0n, BY /leri Pin/I1 s WAM/22% 's ab? ATTORNEYS l Patented Sept. 22, 1936 ,PATENT OFFICE VACUUM TREATMENT 'oF METALS Jesse 0. Betterton and Albert J. Phillips, Me-

`tuchen, N. J., assignors to American Smelting and Reiining Company, New York, N. Y., a corporation of New vJersey f Application October 12, 1933, Serial No. 693,238

4 claims.' (ci. 26e-s4) This invention relatesv to the preparation of metals for casting and more particularly to the vacuum treatment of molten metals.

In certain instances, it has been found that by subjecting molten metals toa vacuum the characteristics of the casting'areimproved. For

l example, the casting may be made` particularly free from gases and voids.

i provement on thefinvention described in the co- I of re tubes i1 which may be supported by the The present invention, accordingly, provides an improved method and means for effecting this treatment which is simple, effective and economical and is an impending application ofL Jesse O. Bettertomserial No. 675,149. The invention is particularly adapted to the treatment of non-ferrous metals, such as copper and aluminum, but it may also be applied to the treatment of other metals as will be apparent to a person skilled in' the art.

In accordance with this invention, the metal is melted, preferably in a non-absorbable atmosphrere, and on its way to a casting boxis passed through a vacuum chamber in a form having a. high ratio of surface area to volume so that substantially the entire mass of metal is directly exposed to the action of the vacuum. In certain embodiments of theA invention, the metal is passed through a vacuum'chamber in the form of a thin film or in the form of a fine spray. The invention also consists of certain novel features hereinafter more fully set forth. Although the novel features which are believed to l be characteristic of this invention will be particularly pointed out in the claims appended hereto, the invention itself, as to it's objects and advantages, andthe manner in which it may be carried out, maybe better understood by referring to the following description taken in connection with the accompanying drawings forming a part thereof, in which Fig. 1 is a broken vertical section of a furnace constructed in accordance with the present invention, z

Fig. 2 is a section taken on the line 2--2 of Fig. 1,

Fig. 3 is a similar section to Fig. 2 showing a modied form of vacuum chamber, I

Fig. 3a is a similar section to Fig. 2 showing a further modified form of vacuum chamber,

Fig. 4 is a broken vertical section showing a further modified form of vacuum chamber, and

Fig. 5 is a section taken o n the line 5LB of Fig. 4.

Like reference characters denote like parts in the several figures of the drawings.

In the following description and in the claims various details will b'e identified by specific names for convenience, but they are intended vto be as generic in their application as the art will permit.-`

Referring to the drawings more in detail and particularly to Figs. 1 and 2, the invention is shown as applied to a furnace l comprising side walls il, roof i2 and an end wall i3. The furnace is also provided with a bottom I4 having a lining l of suitable refractory material upon which a bath i6 of molten metal is supported. 4

The furnace may be provided with a plurality side wall l i in any suitable manner and may join with a suitable header I8. Each flue' I1 may be provided with a burner (not shown) by which heat is supplied to the furnace. An auxiliary burner 2,0 may be mounted in the end wall i3 to assist in raising the temperature of the furnace, for example, in starting the melting operation. A pipe 2| may alsov be provided for supplying 'a chemically inert, non-absorbable gas to the furnace which may be controlled by suitable means, such as a valve 22. .Y

It is tobe understood that the various parts of the furnace outlined above are of standard construction and that only so much thereof has been described as is essential to a proper understanding as it passes through\the cylinder in the man?" ner to be described.

The cylinder 30 is provided, preferably at its upper end, with a vacuum chamber 3| which communicates by pipe 32 controlled by valve 33 with a suitable source of vacuum (not shown).

. This vacuum chamber 3l includes a. sump 35 able means, such as a pipe 50 controlled by valve 5|, may lbe provided for maintaining a-suitable atmosphere within said casting box. 'I'he casting box may be provided with a tap hole 52 to permitthe box to be drained when it is to be taken out of operation.

In the operation of the above described apparatus, the metal to be melted is supplied to the furnace l0 in any convenient manner and is suitably heated by said furnace while a chemically inert, non-absorbable atmosphere is maintained therein. The pressure is then reduced within the vacuum chamber 3| by applying suction to pipe 32 and a vacuum is produced in the chamber sufiicient to raise the molten metal from the bath I6 through the channel 36 to the sump 35. The metal then fills the sump 35 until it flows over the-inclined surface 39 into the sump 40 in the form of a continuously flowing thin film. The metal in the discharge sump 40 then flows through the channel 4| into the casting box 42.

It is to be noted that the elevation of the edge of .inclined surface 39 above the molten metal within the furnace |0 bears a `definite relation to the barometric height of the metal such thatA the metal will not flow over the surface 39 at a rate to fill the sump 40 beyond a predeter-- A' mined point and thus will nt cut down the effective area of the surface 39 which is essential for rapid degasification action.

The elevation of the metal in the sump 4|) above the metal in the casting box 42 also bears a relation to the barometric height lof the metal such that the level of the metal in the sump 40 lis controlled by the level of the metal in the casting box 42 which is preferably maintained at atmospheric pressure. Consequently, by regulating v the level `of the metal within the casting box by means of the valve 43, the leve'l of the metal Within the sump 4|) may be varied as desired. The casting box preferably has sufficient area to prevent substantial changes in 'the level of the metal contained therein in response to intermittent operation of the valve 43 during casting.l It is obviousV that the metal maybe cast directly from the box 42 or may beapplied to any suitable casting device.

By maintaining a thin lm of;L metal over the inclined surface 39, a large surface area. is provided so that substantially-all parts of the metal are directly exposed to the vacuum within chamber 3|.

and casting operation. 1

In the form of the'invention illustrated in Fig. .n 3, the inclined surface |39 corresponds to the surt face 39 of Figs. 1 and 2 and is fluted to provide-a plurality of depressions |49- over which the lm of metal passes in a film of varying thickness. The apparatus is otherwise identical with that described above. It is obviousJ that the contour fof surface |39 may be varied in any suitable manner so as to increase the area of the film and to reduce the thickness thereof at points intermediate the depressions |40 whereby the entire The removalof the gases from the metal` is thus facilitated and a more efficient and rapid to be limited thereby.

angles thereto as respectively shown by |49 andl |39, various other designs or modifications thereof may be effected in order to expose as large an area of surface as possible to the purifyingaction of the vacuum.

In the form of the invention illustrated in Figs. 4 and 5, the furnace and associated parts are similar in construction with those above described. In this form of the invention, however, the channel 36` terminates in a nozzle 60 which may be of any desired form adapted to produce ane spray or mist as the molten metal is passed therethrough. The nozzle 60 may be formed in a boss 6| located preferably at the center of the vacuum chamber `62 and surrounded by a circular sump'63. The metal from the sump 63 is discharged through a channel |4| similar to the channel 4| above described.

In this form of the invention, the elevation of the nozzle 60 may be somewhat less than the barometric height of the metal in the channel 36 so that the metal will be forced through the nozzle under positive pressure. If the metal contains a considerable amount of dissolved gas, the nozzle may be in the form of 'a simple jet opening inasmuch as the accompanying gases in the metal may serve to atomize the stream Without the use of a special nozzle construction. The nozzle may be formed of graphite or of a special hard pressed carbon or of a molded baked refractory material f or the like.

-tion should be such that the metal Within the sump 63 never reachesthe nozzle 60 to interfere With the operation thereof.

In the operation of this form ofthe invention,

practically the entire mass of metal is exposed to f the action of the vacuum inasmuch as the fine spray of mist presents a maximum surface area and prevents any substantial amount of gas'from remaining occluded within the metal. It has been found that metal thus treated produces castings having'superior characteristics, particularly when the metal is melted and cast in a non-absorbable atmosphere.

While certain specific terms have been used for convenience in describing the present invention, it'is to be understood that the inventionv is not For example, the term vacuum has been employed in describing the chamber 3| and the operation of the apparatus. It is to be understood, however, that the degree of vacuum may be varied as required in each particular instance without departing from the spirit of the invention. It is also to be understood thatv gas in a manner more fully described in the copending application above referred to.

Although certain preferred embodiments of the invention have been shown for purposes of illustration, it is to be understood that the invention is not to be limited thereto but is only to be limited in accordance with the following claims whe'n interpreted in'view of the prior art.

What is claimed is:

1. In combination, a melting furnace and a vacuum treating chamber associated therewith comprising a body member mounted within the influence of the heat of said furnace, said chamber having a lower inclined surface elevated a substantial distance above the level of the metal in said furnace, means to remove said metal from said -furnace and to pass the samein a thin lm over said surface, means to receive the met'al from said surface and means to discharge the metal thus received.

2. In combination with a metal melting furnace and a casting box, Vacuum treating means comprising a body member interposed in said` furnace and having a vacuum chamber, a sump within said chamber and positioned above the level of the metal in said furnace and connected thereto by means of a channel, the elevation of the sump bearing a relation to the barometric height of the metal such that the metal from 5 said bath is raised into said sump by the vacuum within said vacuum chamber, and an inclined surface associated with said chamber and adapted to receive metal overiiowing from said sump in the form of a thin lm.

3. In combination with a metal melting furnace and a casting box, vacuum treating means comprising va body member interposed in said furnace and having a vacuum chamber, a sump positioned in said chamber above the level of the 5 metal in said furnace and connected thereto by means of a channel, the elevation of the sump I bearing a relation to the barometric heightl of the metal such that the metal from said bath is raised into said sump by the vacuum within said l0 vacuum chamber, an inclined surface associated with said chamber and adapted to receive metal overowing from said sump in the form of a thin lm, and a second sump adapted to receive metal from said surface and communicating with said l5 casting box, the elevation of saidsecond sump above said casting box having such relation to the barometric height of the metal that the metal in said second sump is maintained at an elevation below said inclined surface.

' 4. An apparatus for treating molten metals comprising a body member forming a vacuum chamber, said chamber having an inclined fluted surface comprising spaced depressions, and means for causing the metal to pass over said 25 surface across said depressions in a film the thickness of which is reduced between said` depressions.

JESSE O. BE'I'IERTON.

ALBERT J. PHILLIPS. 30 

